Limit switch



Sept. 4, 1951 s. K. CARLSON LIMIT SWITCH Filed Oct. 28, 1950 i atenteci Sept. 4, 1951 UNITED STATES PATENT OFFICE.

LIMIT SWITCH Gale K. Carlson, Dixon, 111.

Application October 28, 1950,; Serial No. 192,677

I, My invention relates to limit switches. More particularly, myinvention relates to an improvement in limit switches whereby the same are made simply and accurately adjustable. My invention has particular utility as an electric-door operator, such as an overhead garage door operator.

It is'an object of'my invention to produce a simply constructed limit switch with a minimum of movable parts, which is, nevertheless, fully adjustable. It is another object of my invention to develop a limit switch mechanism in which each limit is separately and accurately adjustable. It is a further object of my invention to provide a means of adjusting a limit switch which does not involve the necessity of opening the case containing the limit switch nor the necessity of shutting off the current to the switch. It is a still further object of my invention to produce an. adjustable limit switch which will hold its precise setting without the necessity of using lock nuts or similar fastening means. Other specific objects and advantages will appear as the specification proceeds.

In general, my invention, which substantially achieves the above objects, comprehends the making of the switches movable bypivotally mounting the switches and associating therewith a threaded adjusting rod. -My invention also involves the placement of the adjusting rod in tension by placing a compression spring thereon. In addition, my invention includes extending the adjusting rods beyond the base of the limit switch and adapting the end portion of the adjusting rod so that they may be easily turned.

My invention is illustrated, in a preferred embodiment, by the accompanying drawing in which- Fig. l is a plan view of my adjustable limit switch showing the structure below the base as hidden objects; Fig. 2 is a broken bottom view showing a portion of the structure above the base as hidden objects; Fig. 3 is a broken side elevational view taken in section on line 3-3 of Fig. 2; and Fig. 4 is a perspective view of the parts forming the adjusting rod and switch prior to assembly.

In the various figures of the drawing, like reference numbers designate like parts.

It will be understood that the structure of the left and right switches together with their adjusting rods is identical. For purposes of simplicity of description, however, the reference numbers have been made to refer only to the 4 Claims. (01. 200-47) 2 I switch on the right in Fig. 1 which is shown on the left in Fig; 2

In the illustration given, I designates a frame or base formed of a suitable metal or other material having attached thereto a threaded shaft M, rotating in bearings l9, and-having traveling thereon operating nut or member l6. Operating nut I6 is equipped with guide finger I! which rides on guide shaft 15 and contact finger l8 which extends in the other direction. A gear or sprocket I3 is attached to the end of threaded shaft l4 whereby the shaftmay be caused to rotate, asior example, by an electric motor. It

will be apparent that other means for actuating shaft I4 can be used, suchas' a slip-on coupling with a threaded shaft.

Block 2 is pivotally mounted on frame I by pivot'screw 3 which is fastened below frame t by nut 4. If desired, a washer or other device can be used to make block 2 moreeasily rotatable, or a pin may be used instead of a screw. Mounted on block 2 is a switch, preferably a micro-switch, having terminals 1, stationary contact 5, and movable contact'arm 6. If a micro switch is used as I prefer, a very: slight pressure on contact arm 6 is suflicient to actuate the switch. Since the details of micro-switch con-' struction are well known, it-is not believed necessary'to further elaborate them here.

Sliding pin or screw 8 is located at the other end of block 2 from pivot screw 3. Sliding pin 8 is secured in block 2 and extends through the curved or arcuate slot 9 in frame I. Beneath frame I, sliding pin 8 is secured into dog l2. Threaded adjusting rod I!) having screw head 2| extends through end flange 20 of base I and threadedly engages dog l2. Compression spring II is located on adjusting rod In between end flange 20 and dog 12. It is apparent that the exterior end of adjusting rod I 0 now shown as screw head 2| can be modified in variousways to facilitate the turning of adjusting rod Hi, such as by forming thereon a knurled nob or a head shaped to fit a wrench.

By inserting a screw drive in screw head 2|, adjusting rod 10 may be rotated in either direction, thus causing dog l2 to respectively advance or retreat upon adjusting rod 10. This motion of dog I2 is communicated by sliding pin 8 riding in curved slot 9 to block 2, and thereby causes block 2 to pivot on screw 3. The pivoting of block 2 produces a displacement of movable contact 6, since it is secured to block 2. Compression spring ll holds adjusting rod ID in tension, and

thereby provides for the maintaining of the exact setting of movable contact 6.

The rotation of threaded shaft l4 by gear l3 causes operating nut I6 to travel to the right as viewed in Fig. 1. After a predetermined number of revolutions, contact finger l8 of operating nut IE will engage movable contact 6 and press against it. This pressure will be transmitted to contact 5, and will thereby close an electric circuit inside of the micro-switch and stop the rotation of shaft l4. v

The switch on the left in Fig. 1 operates in exactly the same way as the switch on the right which has just been described. Its purpose is to limit the transversing of the operating member to the left on threaded shaft I4. Thus the movable contact arms of the two switches limit the travel of operating nutllfi in either direction at a predetermined point selected by turning the adjusting rods.

While in the foregoing specification I have shown my limit switch structure in great detail and in a specific arrangement for illustration, it will be understood that such arrangement and details of the structure may be varied widely by those skilled in the art without departing from the spirit of my invention.

I claim:

1. In a switch mechanism characterized by an operating nut traveling on a rotatable threaded shaft, a frame with two blocks pivotally mounted thereon over arcuate slots in said frame, switches including movable contact arms secured to said blocks, said arms positioned to engage said operating nut when said nut hastraveled a predetermined distance in either direction, dogs secured to said blocks by pins through said slots, and adjusting rods having a compression spring thereon threadedly engaging said dogs, said rods extend ing outside of said frame, and terminating in turning means, wherebysaid rods can be turned and thereby position said, movable contacts to limit the travel of said operating nut.

2. An adjustable limit switch comprising a base aligned with a threaded shaft traversed by an operating member upon rotation of said shaft, two electric switches rotatably connected to said base, said switches including movable arms positioned to alternately contact said operating member upon traversing a predetermined distance in either direction, and adjusting rods under spring tension threadedly rotating said switches, whereby said movable arms can be positioned to engage said operating member at a selected point on its line of traverse in each direction.

3. An adjustable limit switch comprising a base, a threaded shaft mounted in bearings attached to said base, a guide shaft aligned with said threaded shaft, an operating nut traveling on said threaded shaft, said nut including a guide finger resting ori said guide shaft and a contact finger extending in the other direction, two blocks pivotally mounted over curved slots in said base, micro-switches secured to said blocks, said switches including movable arms positioned to engage said contact finger when said finger has rection, dogs secured to said blocks by pins extending through said slots in said base, and rods including a compression spring thereon threadedly engaging said dogs, said rods extending beyond said frame and terminating in a turning. adaptation, whereby said rods can be turned and thereby rotate said blocks to separately po-v sition said contact arms.

4. An adjustable limitswitch comprising a base adjacent to a threaded shaft traversed by an operating member upon rotation of said shaft, two electric switches rotatably connected to said base, said switches including arms adapted to actuate said switches when pressure is applied thereto and being positioned to' be alternately contacted by said operatingjmember upon said operating member traversing a predetermined distance in either direction, and adjusting rods,

threadedly rotating said switches, whereby said arms can be positioned to engage said operating member at a selected point onitsline of.

traverse in either direction.

GALE K. CARLSON..

REFERENCES ICVITED The following references are of record in the Landenberger Aug. 2, 1932. 

